JPS6220707A - Fluid spring type suspension device - Google Patents

Abstract

PURPOSE:To reduce the volume decrease coefficient of an air chamber during bounding, by a method wherein the outer shape of a shell, having a smaller outer size, of an upper shell and a lower shell, is formed such that a portion ranging from the stroke neutral position of a buffering device to the bound side is decreased in size. CONSTITUTION:A shock absorber is displaced to the bound side from the stroke neutral position of the shock absorber shown in a drawing, and when the outer tube 1 side is moved to an upper part in a drawing, a lower shell 17 is also moved upward, and a relative position between a rolling diaphragm 16 and a lower shell 17 is as shown by a one dot chain line. In which case, a tapered part 17c, the size of which is gradually decreased toward a lower part thereof, is formed on the lower shell 17, and since the folded part of the rolling diaphragm 16 is moved over the tapered part 17c, an effective size D thereof is fluctuated in the direction of a decrease. This reduces volume decrease coefficient, enables control of an increase rate of a pressure in an air chamber, and permits improvement of durability of the rolling diaphragm.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a fluid spring type suspension device for a vehicle that uses a fluid spring instead of a metal spring.

[Conventional technology]

As a conventional air spring type suspension device, there is one described, for example, in Japanese Utility Model Application Publication No. 60-46406.

The shock absorber includes a shock absorber that is interposed between the vehicle body and the wheels, with the upper piston rod of the shock absorber being elastically supported by the vehicle body side member and the lower part of the cylinder tube being supported by the wheel side member, and this shock absorber being built-in. A lower shell that is fixed to the outside of the outer tube and extends upward, an upper shell that is fixed to the top of the piston rod and extends downward, and is folded back halfway in the axial direction and one end is airtightly fixed to the bottom of the upper shell. and a rolling diaphragm whose other end is hermetically fixed to the upper part of the lower shell to define an air chamber therein. The air chamber is connected to an external air pressure source through an air supply/discharge port provided in the upper shell, and high-pressure air generated by the air pressure source is supplied to the air chamber to increase the pressure, thereby raising the vehicle height. In addition, by removing air from the air chamber and lowering its pressure, the vehicle height can be lowered.

[Problem that the invention seeks to solve]

However, in such conventional air spring suspension devices, the outer diameter of the lower shell is a constant straight shape in the axial direction, and the volume inside the rolling diaphragm is proportional to the relative displacement of the shock absorber. Because the structure was designed to increase and decrease over time, when the air chamber bounces, the volume of the air chamber decreases, causing a significant increase in internal pressure. There was also the problem of poor sex.

[Means for solving problems]

This invention was made by focusing on such conventional problems, and includes a shock absorber interposed between a vehicle body and a wheel, an upper shell fixed to an upper part of a piston rod of this shock absorber, A lower shell is attached to a member on the cylinder tube side of the shock absorber, and the lower shell is folded back at a midway point in the axial direction, and one end is airtightly fixed to the lower shell and the other end is fixed to the upper shell to form a fluid chamber therein. and an elastic cylindrical body defining an outer diameter of the lower shell or the upper shell with a smaller outer diameter on the bound side from the neutral position of the stroke of the shock absorber. By doing so, the above-mentioned problems are solved.

[Effect]

Therefore, in this invention, the outer diameter shape of the lower shell or the upper shell having the smaller outer diameter to which one end of the rolling diaphragm, which is an elastic cylinder, is fixed airtightly is
- By making the bounce side smaller in diameter from the neutral position of the stroke of the shock absorber, when bouncing, the effective shape of the rolling diaphragm is made smaller, the volume reduction rate on the bounce side is reduced, and the pressure increase in the fluid chamber is suppressed.

〔Example〕

The present invention will be explained below based on illustrated embodiments.

1 to 3 illustrate an embodiment of the present invention, and are diagrams showing essential parts of a front suspension for an automobile.

First, to explain the structure, 1 shown in FIG. 1 is an outer tube that is a member on the cylinder tube side, and a shock absorber is housed inside this outer tube 1, and a piston rod 3 of the shock absorber.
extends upwardly through the center of the lid 2 screwed onto the upper end of the outer tube 1.

The upper part of the piston rod 3 has a large diameter part 3a, a medium diameter part 3b, and a small diameter part 3c formed by two stepped parts.
A cylindrical bump stopper 4 made of a rubber-like elastic body is press-fitted onto the top of the large diameter portion 3a, and a central hole 5 of an upper shell 5 is placed above the bump stopper 4.
The piston rod 3 also passes through a. The hole 5a of the upper shell 5 has a large diameter hole and a small diameter hole formed by a stepped portion, and the large diameter hole has a large diameter portion 3a of the piston rod 3.
However, the medium-diameter portions 3b of the piston rod 3 fit into the small-diameter holes, and a hole provided at the upper end of the large-diameter portion 3a, as shown in FIG. 2, is parallel to the plane passing through its axis. As shown in FIG. 3, the piston rod 3 and the upper shell 5 are connected by engaging the convex portion 7 that matches the notch 6 formed in the large diameter hole with the notch 6 in which the flat surface is formed. They are integrated in the direction of rotation by preventing relative rotation between them.

8 is a sealing member.

A bearing 9 is fitted onto the medium diameter portion 3b of the piston rod 3 above the upper shell 5, and the bearing 9 and the upper shell 5 are connected to the piston rod 3 by a nut 10 screwed into a male screw provided in the small diameter portion 3C. It is tightened and fixed. The inner cylinder 1) is disposed outside the bearing 9, and its lower end is caulked to make the inner cylinder 1) and the outer ring of the bearing 9 integral in the rotational direction.

An outer cylinder 12 is arranged concentrically on the outside of the inner cylinder 1), and both the inner and outer cylinders 1). A ring-shaped mount insulator 13 is interposed between the mount insulators 12, and the inner peripheral surface of the mount insulator 13 is fixed to the inner cylinder 1), and the outer peripheral surface thereof is fixed to the outer cylinder 12 by vulcanization adhesive or the like, so that they are integrally formed. The outer cylinder 12 is
The piston rod 3 is attached to the vehicle body side member 15 by bolts 14 fixed to the lower flange, and in this way, the upper end of the piston rod 3 is elastically supported on the vehicle body side.

The upper shell 5 is composed of a disc-shaped upper plate 5b provided with the hole 5a, and a cylindrical side plate 5c extending downward continuously from the outer peripheral edge of the upper plate 5b. One end of a rolling diaphragm 16, which is an elastic cylinder, is fitted onto the opening side of the side plate 5C. The rolling diaphragm 16 is made of a rubber-like elastic material such as rubber, and is formed into a cylindrical shape with different diameters at both ends in the axial direction, and is folded back in the middle so that both ends can be relatively displaced in the axial direction. There is. The end of the rolling diaphragm 16 on the small diameter side is fitted onto a lower shell 17 that is airtightly fixed to the outside of the outer tube 1.

The lower shell 17 has a cylindrical shape, and is formed between a large diameter part 17a into which the rolling diaphragm 16 is fitted, a small diameter part 17b fixed to the outer tube 1, and between the large diameter part 17a and the small diameter part 17b. The large diameter portion 17a is disposed toward the upper shell 5 side. Then, each end of the rolling diaphragm 16 is
Clip bands 1 are attached to the side plate 5C and the large diameter portion 3a, respectively.
It is tightened and fixed airtight with 8°19. This rolling diaphragm 16, upper shell 5 and lower shell 1
A gap defined by 7 constitutes an air chamber 20 which is a fluid chamber.

The air chamber 20 is connected to a fluid pressure device (not shown) through a supply/discharge port 21 attached to the side plate 5C of the upper shell 5, and the air chamber 20 is connected to a fluid pressure device (not shown), and the air chamber 20 is supplied with high pressure air to increase its pressure. The height of the vehicle can be increased, and the vehicle height can be lowered by removing air from the air chamber 20 and lowering the pressure.

The lower portion of the air suspension on the outer tube I side is fixed to a knuckle (not shown) that rotatably supports the wheel, and is thus interposed between the vehicle body and the wheel.

Next, the effect will be explained.

Now, assume that the state shown in Fig. 1 is when the stroke of the shock absorber is at the neutral position of relative displacement, and when the shock absorber is displaced from this state to the bound side, the outer tube 1 side moves upward in Fig. 1. ,
At the same time, the lower shell 17 moves upward to approach the upper shell 5. Therefore, the rolling diaphragm 16 is displaced relative to the lower shell 17 to the position shown by the dashed line.

In this case, the radius of curvature at the folded portion of the rolling diaphragm 16 is determined by the rigidity of the material forming it, and remains approximately the same at any position regardless of the length of the stroke. In this embodiment, the folded portion is located at the tapered portion 17c provided on the lower shell 17,
The folded portion is made movable along this tapered portion 17c.

Therefore, on the bound side, the effective diameter at the folded portion of the rolling diaphragm 16 becomes smaller depending on the magnitude of the bound, as shown by the dashed line in the figure.

Here, the effective radius refers to the distance between the centers of the radius of curvature at the folded portion of the rolling diaphragm 16,
Let Do be the effective diameter at the neutral position of the stroke, and Di be the effective diameter at a certain relative displacement.

By reducing the effective diameter of the folded portion of the rolling diaphragm 16 in this manner, the volume reduction rate ΔV on the bound side can be reduced.

That is, the volume reduction rate ΔV can be expressed by the following equation.

ΔV=AXS...(1) Here, A: Effective area of effective diameter portion = π(D2-d2)/4...(2) S: Stroke from neutral position Therefore, when bouncing, its effective Since the diameter Di becomes smaller than the effective diameter Do at the neutral position and the effective area At becomes smaller than the effective area Ao at the neutral position, the volume reduction rate ΔV also becomes smaller. In this case, since the relationship PV=constant holds between the volume V of the air chamber 20 and its internal pressure P, by reducing the volume reduction rate ΔV, the rate of pressure increase in the air chamber 20 during bounce can be reduced. The lower shell can be lower than that of a conventional air spring suspension device in which the lower shell has a straight shape.

As a result, the durability of the rolling diaphragm 16 due to the pressure drop in the air chamber 20 and the sealing performance of the air chamber 20 can be improved, and the clip band 18.
Damage to the rolling diaphragm 6 due to the damage caused by the rolling diaphragm 6 can be suppressed. Moreover, when bouncing, the lower shell 17
Since the rolling diaphragm 16 has a small diameter guided by the tapered portion 17C, the clearance between the rolling diaphragm 16 and the tire during bouncing can be increased, and therefore, damage to the rolling diaphragm 16 by the tire can be prevented. I can do it.

In this embodiment, the piston rod 3 is provided with a notch 6, and the upper shell 5 is provided with a convex portion 7 that engages with the notch 6, and the notch 6 and the convex portion 7 are made to coincide with each other. Since it is integrally formed with the piston rod 3 in the rotational direction, when tightening the nut 10 during assembly, the nut 10 can be tightened by fixing the upper shell 5 without directly fixing the piston rod 3. Therefore, it is not necessary to prevent the piston rod 3 from rotating by providing a width across flats for engaging a spanner or the like in the small diameter portion 3C at the upper end of the piston rod 3 having the smallest diameter, as in the conventional case. Deformation of the shaft in the width across flat portion can be prevented.

FIG. 4 shows another embodiment of the invention.

In this embodiment, the outer diameter shape of the lower shell 27 on the rebound side from the neutral position of the stroke of the shock absorber is
It is a straight type with the outer diameter dimension equal to the neutral position.

That is, FIG. 4 shows a state in which the relative displacement of the shock absorber is at the neutral position of the stroke, and at this time, the folded portion of the rolling diaphragm 16 changes from the large diameter portion 27a of the lower shell 27 to the tapered portion 27c. It is set to be located in the part. The other configurations are the same as those in the previous embodiment.

In this embodiment, unlike the embodiment shown in FIG. The spring reaction force caused by this can be made smaller than that in the above embodiment. As a result, it is possible to reduce the full extension shock of the suspension, that is, the shock at the time of collision between the rebound stopper provided in the shock absorber and the stop rubber that comes into contact with the rebound stopper to limit the maximum stroke on the extension side.

In addition, in the above embodiments, the lower shell is 17.27 mm.
Although the side is made small in diameter, the present invention is not limited to this.
Of course, a tapered portion similar to 7c may be provided and the folded portion of the rolling diaphragm 16 may be displaced along the upper shell. Further, although air is used as the fluid, it goes without saying that other gases may be used.

〔Effect of the invention〕

As explained above, according to the present invention, the outer diameter shape of the shell with the smaller outer diameter among the lower shell or upper shell to which one end of the rolling diaphragm, which is an elastic cylinder, is fixed airtightly is adjusted to the stroke of the shock absorber. Since the diameter is smaller on the bound side from the neutral position of the stroke, when the elastic cylinder is bound, the effective diameter at the folded portion can be made smaller than the effective diameter at the neutral position of the stroke. Therefore, during bouncing, the volume reduction rate of the fluid chamber due to the relative displacement of the shock absorber can be reduced, and the rate of pressure increase in the air chamber due to bouncing can be made lower than in conventional air spring type suspension devices. As a result, it is possible to improve both the durability of the elastic cylinder based on the pressure drop in the fluid chamber and the sealing performance of the fluid chamber. In addition, since the effective diameter of the elastic cylinder becomes small when bound, the clearance between the elastic cylinder and the tire on the bound side can be increased, and damage to the elastic cylinder by the tire can be prevented. You can also get the effect of being able to do it. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of an embodiment of the present invention, and FIG.
The figure is a perspective view showing the main part of the piston rod according to the present invention, FIG. 3 is a perspective view showing the main part of the upper shell,
FIG. 4 is an explanatory diagram showing another embodiment of the present invention. 1... Outer tube, 3... Old piston rod, 5... Upper shell, 6... Notch, 7... Protrusion, I5... ...Vehicle body side member, 16...Rolling diaphragm (elastic cylinder), 17.27...Lower shell, 17c, 2
7c・・・Taber part, 20・Old・Air chamber (fluid chamber)

Claims (3)

[Claims] (1) A shock absorber interposed between the vehicle body and the wheels, an upper shell fixed to the upper part of the piston rod of the shock absorber, a lower shell attached to the member on the cylinder tube side of the shock absorber, and a shock absorber disposed in the axial direction. A fluid spring type suspension device comprising: an elastic cylindrical body that is folded back in the middle and has one end fixed to the lower shell and the other end hermetically fixed to the upper shell to define a fluid chamber therein, A fluid spring type suspension device, wherein the outer diameter of the shell having a smaller outer diameter among the lower shell or the upper shell is set to a smaller diameter on the bounding side from the neutral position of the stroke of the shock absorber. (2) The outer diameter of the shell on the smaller outer diameter side of the lower shell or the upper shell is a conical shape that becomes smaller as it moves away from the other shell. The fluid spring suspension device described. (3) The outer diameter shape of the lower shell or upper shell is
The fluid spring type suspension device according to claim 1 or claim 2, wherein the stroke has a straight shape having an equal diameter from the neutral position to the rebound side.